Urban surveillance key to tackling insect invaders

The
discovery of five previously undetected insect species in
urban areas has prompted a recommendation to increase
surveillance efforts for invasive invertebrates.

Tiny
insect invaders can be a major threat to New Zealand’s
environment, and the volume of our international trade and
travel means our borders cannot be made totally secure.
Surveillance is usually targeted at specific pests such as
the Asian gypsy moth. However, there is no generalised
surveillance in urban areas that may harbour “sleepers” –
species that have established but are not yet widespread.

Landcare Research scientist Richard Toft is researching
the prevalence of introduced insects in urban habitats, and
whether any have established here undetected. At the same
time he has been trialling a range of traps, from sticky
traps to tent-like “malaise” traps, to see which are most
efficient and cost-effective for sampling invasive
invertebrates.

Mr Toft and his team trialled traps at the
Port of Nelson, and around The Warehouse distribution centre
at Wiri in Auckland. He also coordinated malaise trap
surveys in suburban gardens in Christchurch, Nelson and
Wellington.

Two new introduced beetle species were
discovered at Wiri, and are in the process of being
identified. Three new introduced species of fungus gnats
(small flies) were recorded in suburban gardens. One was
very abundant, and is now believed to have been here for
more than 20 years. It is not yet known what effect these
gnats may have on native ecosystems.

In some typical
backyard gardens, half of the moths and 80% of beetles found
were introduced species.

At the Port of Nelson, a new
ant incursion (an Australian ant, Mayriella sp.) was
detected, reported to the Ministry of Agriculture and
Forestry (MAF), and subsequently eradicated. Invaders were
also discovered in new places; for example, various ant
species were recorded for the first time in Nelson or the
South Island.

“It is clear that we need to be better aware of
what insects are getting here. By way of further
illustration, since MAF began surveillance around ports for
red imported fire ants in 2002 they have discovered two new
introduced ant species established here and have launched
incursion responses against six others, as well as detecting
an incursion of red imported fire ant at Napier.

“New
Zealand has some of the strictest biosecurity measures in
the world, but unless we search every square centimetre of
every container, detecting all invaders at the border is
simply not possible. We need better post-border
surveillance, to detect any invaders that have made it past
the border, most likely into surrounding suburban areas.

“As suburban areas are usually highly modified and have
many introduced plants, they are ideal reservoirs for
introduced species, both known and unknown. If we can detect
invertebrate pests in their ‘lag’ stage, we can still
eradicate them before they threaten our native
ecosystems.”

Mr Toft says catching pests at this stage is
usually far more cost-effective than battling pests that are
well established. “For example, the current effort to
eradicate fire ants around Brisbane is costing tens of
millions of dollars per annum.” Additionally, having a
better knowledge of the variety of invertebrate invaders we
have reduces the risk of unwittingly spreading these pests
to other countries.

Plans for future research include
further identification work on the insect specimens
collected during the surveys and continued development of
potential surveillance techniques. There will also be work
on some of the existing urban “sleepers” to better determine
their potential threat to the environment.

Mr Toft says
the public can play a vital role in biosecurity by keeping
an eye out for the unfamiliar.

“The public are actually
very good at detecting larger invertebrate pests and the
small ones that make a big nuisance. The painted apple
moth, the tussock moth, the Australian saltmarsh mosquito,
and the fire ant colony at Auckland were all first detected
here by members of the public.”

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